Diamond hard coating of ferrous substrates

ABSTRACT

The present invention relates to hard coating of ferrous metal substrates using a laser beam with diamond particles in a metal matrix produced from precursor powders of metals which bond to the diamond particles and to the ferrous substrate. The hard coating is particularly useful for white iron castings for pumps ( 200 ) used in piping tar sand and water mixtures.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

STATEMENT REGARDING GOVERNMENT RIGHTS

Not Applicable

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a process for laser beam hard coatingof a ferrous metal substrate with diamond particles in a metal matrix.In particular, the present invention relates to hard coating a cast ironarticle, particularly a white iron casting, in order to improve theabrasion resistance of the coated surfaces of the article. Moreparticularly the present invention relates to pumps having hard coatedsurfaces of the pump which are in contact with an abrasive water and tarsand mix.

(2) Description of the Related Art

The prior art has described processes for using nozzles providing aparticle spray and a laser beam for applying a hard faced surfacecoating to a ferrous substrate. U.S. Pat. No. 4,724,299 to Hammeke andU.S. Pat. No. 6,316,744 to Nowotny et al are illustrative of the patentart. The disclosures of these patents are incorporated by referenceherein in their entireties. In general, a powdered mixture of a metalalloy with particles of a hard material are coated on a substrate bymelting the particles of the metal alloy on a spot surface of thesubstrate irradiated by the laser beam. Diamonds have been used incutting tools as evidenced by U.S. Pat. Nos. 6,176,888 and 6,238,280 byunrelated processes.

Diamond particles have been incorporated into a metal alloy in the pastin an attempt at providing a hard coating in parts which arecontinuously abraded by hard particles. The problem is that there is apoor bond between the diamond and the metal alloy when abraded by sandparticles in an aqueous slurry. The result is that when abraded thediamond particles come loose from the coated surface. There is a needfor an improved hard coating process and the resulting products.Relevant prior art is DE10024155 (which corresponds to EP1155768).

OBJECTS

It is therefore an object of the present invention to provide a lasercladding or hard coating process which enables bonding of the surface ofthe diamond particles to the metal alloy and bonding of the ferroussurface to the metal alloy in such a way that the hard coating isresistant to abrasion, particularly by sand particles. It is also anobject of the present invention to provide a process which is economicaland reliable and capable of being automated with robotics and CNCcontrolled machines or devices. These and other objects will becomeincreasingly apparent by reference to the following description.

SUMMARY OF THE INVENTION

The present invention relates to an article of manufacture which is aferrous substrate comprising carbon which requires a hard faced surfacecoating to reduce wear in use; and a layer of a composite which providesthe hard faced surface coating comprising diamond particles in a metalmatrix which is bonded on the diamond particles, and wherein the layeris bonded to the substrate. Preferably the diamond particles are betweenabout 40 and 100 microns in their largest dimension. Preferably thematrix comprises copper, tin and titanium. Preferably the matrixconsists essentially of about 60 to 80% by weight copper, 15 to 25% byweight tin and 5 to 20% by weight titanium. Preferably there is aplurality of overlapping layers on the substrate wherein each layer is40 to 80% of a single track width. Preferably the substrate is a castingof white iron or a steel comprising about 4% by weight or less of thecarbon. The diamond particles can be naturally or synthetically derived.

The present invention also relates to a process for providing an articleof manufacture with a hard faced surface coating which comprises:providing a ferrous substrate containing carbon and requiring a hardfaced surface coating; feeding a particulate mixture of diamondparticles and separating metal particles which can be melted to providea matrix around the diamond particles into a heating zone whileimpacting the mixture with a laser beam in a non-reactive atmosphere soas to form the hard faced surface coating as a layer bonded to substrateand the diamond particles. Preferably the process is conducted at atemperature between 400 and 900° C. Decomposition of the diamondparticles at high temperature is avoided due to the low heat input ofthe laser process and the rapid cooling of the clad layer. Preferablythe metal particles comprise copper, tin and titanium. Preferably thediamond particles comprise 30 to 50% by volume of the metal particles.Multiple of the layers can be formed on the substrate, although this isnot preferred. Preferably the substrate is a white iron or a steelcomprising 4% or less by weight of the carbon. Preferably the atmosphereis argon. Preferably particles are applied through moving a head orarticle which is robotically driven or a CNC controlled system, whichhead supplies the particles and the laser beam on the substrate in acontinuous stream so that the layer is applied as adjacent overlappinglines on the substrate.

The present invention also relates to an apparatus for hard facedsurface coating a ferrous metal substrate containing carbon whichcomprises: a first support means for holding the substrate; a supplymeans mounted on a second support means adjacent the first support meansfor supplying diamond particles with particles of a metal matrix ontothe substrate in a heating zone which is heated by a laser beam toprovide the heat, wherein the first and the second support means areadjacent to each other and moveable relative to each other and whereinin use the laser beam bonds the diamond particles onto the substrate ata temperature controlled so as to not degrade the diamond particles toprovide the hard faced surface coating in the metal matrix as the hardfaced surface coating. Preferably the first support means is moveableand mounts a head for supplying the laser beam and the particles and thesecond support means is fixed. Also the article can be moved relative tothe laser beam.

The present invention also relates to an improvement in a pumpcomprising a rotatable fluid impeller and a housing supporting animpeller for rotation in the housing for the pumping, which comprises atleast one surface inside of the pump with a hard faced surface coatingwhich engages the fluid to be pumped, wherein the surface which iscoated comprises a ferrous composition comprising carbon and whereincoating comprises a layer of a composition comprising diamond particlesin a metal matrix which is bonded to the diamond particles, and whereinthe layer is bonded to the substrate. Preferably a face of an inletplate which diverts flow of the fluid to the impeller has the hard facedsurface coating. Preferably the pump comprises a white cast iron.Preferably the housing, the impeller and a diverter plate in the inletof the pump comprise the hard faced coating. The pump parts which areworn in use by abrasion can be hard coated and reused. The coating isalso resistant to impact by particles in the fluid.

The present invention further relates to an improvement in a method ofpumping a fluid containing abrasive particles, which comprises:providing a pump comprising a rotatable fluid impeller and a housingsupporting the impeller for the rotation in the housing for pumping,wherein at least one surface in the pump which engages the fluid to bepumped has a hard faced surface coating, wherein the surface which iscoated comprises a ferrous composition comprising carbon and wherein thecoating comprises at least one layer of a composition comprising diamondparticles and a metal matrix bonded to the diamond particles, andwherein the layer is bonded to the substrate; pumping the fluid in thepump, wherein the layer of the coating inhibits erosion by the abrasiveparticles. Most preferably the abrasive particles are in a tar sandwhich is transported in an aqueous solution from a mining site. Mostpreferably the pump comprises cast white iron on the surfaces in contactwith the fluid and abrasive particles. Preferably portions of thehousing, the impeller and a suction liner for an inlet of the pumpcomprise the hard face coating.

The present invention also relates to an improvement in a pumping systemcomprising a rotatable fluid impeller and a housing supporting theimpeller for the rotation in the housing for pumping and piping, whichcomprises at least one surface inside of the pump and optionallyportions of the piping in the system with a hard faced surface coatingwhich engages the fluid to be pumped, wherein the surface which iscoated comprises a ferrous composition comprising carbon and whereincoating comprises a layer of a composition comprising diamond particlesin a metal matrix which is bonded to the diamond particle, and whereinthe layer is bonded to the substrate. Preferably a face of an inletplate which diverts flow of the fluid to the impeller has the hard facedsurface coating.

The present invention also relates to an improvement in a method ofpumping a fluid in a pumping system containing abrasive particles, whichcomprises: providing a pump in the pumping system with piping comprisinga rotatable fluid impeller and a housing supporting an impeller for andoptionally portions of piping in the system the rotation, wherein atleast one surface in the pump and optionally portions of piping in thesystem which engages the fluid to be pumped has a hard faced surfacecoating, wherein the surface which is coated comprises a ferrouscomposition comprising carbon and wherein the coating comprises at leastone layer of a composition comprising diamond particles and a metalmatrix bonded to the diamond particles, and wherein the layer is bondedto the substrate; pumping the fluid in the pumping system, wherein thelayer of the coating inhibits erosion by the abrasive particles. In thepreferred use of the system the abrasive particles are in a tar sandwhich is transported in an aqueous solution from a mining site. FIGS. 3,4, 5 and 6 show the preferred pump and parts which are hard coated bythe present invention. The dotted areas are the hard coatings. Theprocess is effective at higher temperatures (more than 600° C.) becauseof the big heat sink of the ferrous metal parts and the comparable lowheat input by the laser. Thus there is a rapid cooling for laser beamcladding.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows a longitudinal cross-sectional view of a preferred head ornozzle for delivering particles of the alloy and diamonds as well as alaser beam onto a ferrous substrate to produce a hard coating on thesubstrate.

FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1.

FIG. 3 shows a pump impeller 100 with the hard faced coating (dots) onthe edges of vanes 100A (arrow).

FIG. 4 is a perspective view of a hard coated suction liner 101 whichoptionally faces into an inlet of a pump.

FIG. 5 is a perspective view showing a schematic of a pump housings 102which has an inlet having the hard faced coating 102A (dots).

FIG. 6 is a cross-sectional view of an assembled pump showing the partsof FIGS. 3 to 5 in position in the pump.

FIG. 6A shows piping to the pump with a diamond hard coating (dots).

FIG. 6B is a perspective separated view of the pump 200 showing theposition of the coated parts.

FIG. 7 is a perspective view showing a hard coating apparatus used inthe Examples.

FIG. 8 is a perspective view of a commercial conical nozzle 50 of thetype shown in FIG. 1. The connectors are for cooling water 53, powderand argon carrier gas 52 and extra gas shielding around the nozzle tip51.

FIG. 9 is a side view of overlapping layers 60 of the hard faced coatingproduced in the Examples.

FIG. 10 is a perspective view of a robotic apparatus with the nozzle ofFIG. 9 for coating the pump parts of FIGS. 3, 4 and 5 for instance.

FIGS. 11A and 11B are microscopic cross sections of a diamond hardcoating with matrix material CuSn20Til3 The diamonds show as black. Theparticles were natural diamond with a mesh size of about 100.

FIG. 12 is a microscopic plan view of a coating with spaces between thelayers of the hard coating as an imperfection corrected by overlappingthe layers as in FIG. 9.

FIG. 13 is a graph showing a progression over a period of several monthsof improved mean abrasion test results on various samples over timeleading to the 0.02 mass loss with ASTM 65 which uses dry sand and arubber wheel.

DESCRIPTION OF PREFERRED EMBODIMENTS

Apparatus

A preferred coating head is shown in FIGS. 1 and 2 of U.S. Pat. No.6,316,744. The apparatus is adapted to process diamond and matrix metalalloy particles. A housing which is formed from two parts 4, 5 is used,which parts are connected to one another by means of a screw thread 9,with the possibility of fixing the parts in a specific position by meansof an additional locking nut 10. The screw thread 9 can be used todisplace the two parts 4 and 5 of the housing relative to one another,resulting in telescopic displacement parallel to the longitudinal axisof a laser beam 7.

Using a beam-guiding means and, if appropriate, also a beam-shaping unit(not shown here), the laser beam 7 can be directed through the housingpart 4 onto the surface of a diagrammatically depicted workpiece. Thefocusing of the laser beam 7 is set in such a way that a specific beamspot size can be obtained on the surface of the workpiece, approximatelycorresponding to the size of a focal point of a hollow powder jet. Ascan be seen from FIG. 1, the focus of the laser beam 7 may also bearranged inside the housing of the machining head.

An inert gas can be guided through the housing part 4 onto the surfaceof the workpiece in addition to the laser beam 7, which on the one handallows improved cooling and on the other hand is able to preventdroplets which splash up from the surface from penetrating into thehousing.

Both the part 4 and the part 5 of the housing are in this exampledesigned with rotational symmetry about the longitudinal axis of thelaser beam 7. A turbulence chamber 1, which surrounds the part 4 of thehousing and into which radially opposite entry openings 11 lead in theupper area of the turbulence chamber 1, is formed between part 4 andpart 5 of the housing. A powder-gas flow can be guided into theturbulence chamber 1 through each of the entry openings 11, and thepowder components, which may be different, can be mixed inside theturbulence chamber 1. The bottom part of the turbulence chamber 1 is ofconically tapering design, and an angle of inclination of the cone whichprevents powder particles from sticking to the inner wall should beselected.

In this embodiment, the turbulence chamber 1 leads into an inlet funnel8, in which, in turn, there are entry openings for stabilizing passages2. As can be seen from FIG. 1, the stabilizing passages 2 are alignedparallel to the longitudinal axis of the laser beam 7, and as can beseen in particular in FIG. 2, they are arranged radially symmetricallyover the circumference, with a constant distance between them. Thepowder together with the carrier gas then passes through the cylindricalstabilizing passages 2 into an annular gap 14 which tapers conicallyinto the direction of the surface of the workpiece. The cone angle ofthe annular gap 14 should be selected here in such a way that thecoaxial hollow powder jet which emerges from the annular gap 14 strikesthe surface of the workpiece with a small diameter, preferably at itsfocal point.

On the housing part 4, there is an exchangeable nozzle tip 6, which inthis case is connected to the housing part 4 by means of a screw thread.At least part of the outer circumferential surface of the nozzle tip 6forms in this case the inner wall of the annular gap 14.

On that side of the housing part 5 which faces the surface of theworkpiece, a conical outer nozzle 3 is present or is formed. This outernozzle 3 may also be an exchangeable design. The inner circumferentialsurface of the outer nozzle 3 then forms the outer wall of the annulargap 14. This design makes it possible to vary the clear width of theannular gap 14 by suitably rotating the two housing parts 4 and 5,resulting in a greater or lesser relative movement of the housing parts4 and 5 with respect to the longitudinal axis of the laser beam 7depending on the corresponding angle of rotation.

One or more cooling passages 12, 12′ and 13, which are connected to oneanother and through which a cooling agent, preferably water, can pass inparticular into the critical part of the machining head, are formed onthe part 5 of the housing and, in addition, on the part 4. The annularcooling passage 13 can cool in particular the inner part 4 with nozzletip 6. The cooling passage 12′ acts in particular on the area of theouter nozzle 3. With this integrated cooling system, it is possible toreadily deal with even the critical heating which is generated byprolonged use.

Process

A “matrix metal alloy” as used herein is one which is based upon amixture of metals which metals melt at elevated temperatures, usuallybetween about 400° to 900° C., without damaging the diamond particles,to produce the hard faced coating. Numerous metal alloys in thistemperature range are available, such as shown in Table 1. TABLE 1Liquidus Soldering process temperature [° C.] Materials Soft soldering<450 Zinc-, Lead- and Tin- solder as well as Tin- Lead-solder metalsHard soldering 450 . . . 900 Silver-, Copper- and Aluminum-basis soldersHigh temperature >900 Nickel-, Copper- and soldering noble metal soldersIn the present invention the preferred metal alloy matrix is a mixtureof copper (Cu) and tin (Sn).

The pumps which are hard coated are preferably made of white ironcastings because of durability and abrasion resistance. The problem isthat the white iron alone is not sufficiently wear resistant when tarsands are being pumped. The term “white iron” refers to a relativelybrittle cast iron that is essentially free of graphite where most of thecarbon is present as hard F₃C, referred to as cementite. White ironexhibits a white crystalline fractive surface because fracture occursalong the iron platelets. When heated over a long period of time, whiteiron becomes malleable iron where the F₃C becomes iron with nodules ofgraphite. A typical composite of a high abrasive white iron is set forthin Table 2. Table 2 shows a typical composition of white iron which is apreferred substrate for hard coating. TABLE 2 Fe C Mn Si P S Cr Ni Cu MoAl Mg CE 70.85 2.78 0.39 1.26 0.042 0.056 23.15 0.46 0.20 0.7781 N/A0.259 N/ABrinnel Hardness on 5 bars: 532, 532, 512, 555, 555

EXAMPLES

A sideways positioned cladding unit cyclone (Fraunhofer IWS, DresdenGermany) as shown in FIG. 7 was used in the Examples. The cyclone nozzletechnical information is commercially available. The TechnicalInformation is as follows:

Application Cyclone to alloy of two powders Optimal grain size 40 to 200μm—other sizes are possible Recommended powder feeding rates 2 to 10g/min to 1 kW laser power; 40 g/min to 3 kW laser power. Minimum powderfocus approximately 3 to 6 mm. Distance nozzle working surface—13 mm.Nozzle tip changeable—diameter 1 to 3 mm (1 steps to 0.5 mm) possible.Maximum laser power—5 kW (diode laser). Higher laser power may decreasethe long-term stability. Compatible laser—CO₂₋, Nd: YAG-, diode laser.Dimensions—height: 100.0 mm minimum height without nozzle top; diameter:50.0 mm. Connection—2 connections for powder feeding, inclined; 1connection for inert gas, inclined; 2 connections for cooling water(flow by room temperature); All connections for flexible tube with 6 mmexternal diameter. Included in delivery —X-Y-Z positioning unit. 1exchangeable nozzle tip couple. An added nozzle for a protection ornon-reactive gas is used

The following specific Examples demonstrate a good bonding of the hardcoating material to the substrate which is white iron, a good contentand distribution of the diamonds in the coating and thus increased wearresistance. FIGS. 11A and 11B show a cross-section of the diamonds inCuSn20Til3 metal matrix where the numbers are percentages by weight. Thediamonds are natural and are 100 mesh size. A main objective of theExamples was to establish different laser parameters, claddingstrategies to achieve strong bonding without damaging the diamondparticles and to increase the wear resistance. The samples of FIGS. 11Aand 11B met the requirements of the G65 wear test (ASTM).

Tests were performed to provide laser clad natural diamond particles inthe copper-tin titanium matrix as shown in FIGS. 11A and 11B. In thesetests it was important to understand the performance of the coating andhow it relates to the percentage of diamond content. The wearperformance and bonding of the diamonds in the matrix is dependent onthe fraction of diamonds in the coating, so this was evaluated on thewhite iron.

As shown in FIG. 7, the process was carried out with a 4.4 kW diodepumped Nd:YAG Rofin-Sinar (Hamburg, Germany) and the beam 21 wassupplied to the work piece via a 400 micron fiber and a 200 mmcollimator with 200 mm focus lens (not shown). The laser beam 21 had avertical position. A powder nozzle 20 supplied the coating powder withArgon as conveying and shield gas. The powder nozzle was located offaxis and in front of the position of the laser beam 21. The direction ofcoating is left to right. The hard coating material was a mixture of thematrix material particles and the diamond particles. Argon gas wassupplied by one or both gas supply nozzles 22.

First, the heat input that was required to fully fuse the matrix to thediamond particles and to the substrate was determined. During the tests,the relative positioning of the coupons (substrate) and the laser beamfocus was optimized.

FIG. 9 shows the resulting cladding or hard coating on coupons(substrate). The cladding direction was on the long and on the shortaxis. The desired coating layer has a height of at least 0.5 mm.

Results

The following Table 3 shows the cladding parameters and for coupons 1 to4. The matrix material was preferably pre-screened (100 mesh) to improvethe powder flow through the nozzle 21. So called “pulsing” occurs whenthe powder is blown into the melt pool. Pulsing causes unstable flowconditions and thus inhomogeneous cladding results. The layer height isparticularly affected. This problem could be reduced by using thisscreening.

Another problem is the shield gas (argon) supply. For this tests 2additional gas supply nozzles 22, one in front and one behind the laserbeam were used. The shield gas supply was through the powder nozzle 20as well as the carrier gas for the diamond particles. Thus oxidation ofthe coating was mainly avoided. However, the front (left) nozzle hassome influence on the powder flow in the melt pool and makes the processunstable. Therefore this nozzle was removed in later tests which solvedthis problem.

The layer height of each coupon was measured before and after cladding.From Table 1 it was learned that the height depends on the powder massflow which is set by the rotation speed for the diamonds and the alloypowder inside of the powder nozzle 20. TABLE 3 Laser: Nd:YAG (400 μmfiber, Focus distance 205 mm, Spot size 3˜4 mm Alloy: CuSn20Ti13premixed, 100-325 mesh size screened Diamond: natural diamonds mesh size100 Double sided shield gas Substrate: White iron, thickness 11.40 mmRotation Rotation Hatch Thickness Diamond Alloy Power F distance [mm][rpm] [rpm] [W] [mm/min] [mm] Coupon 1 After layer 1: 1 2.5 1800 370 212.6 After layer 2: 1 2.5 1800 370 2 13.4 Coupon 2 After layer 1: 1.52.5 1700 370 2 13.0 After layer 2: 1.5 2.5 1700 370 2 14.0 Coupon 3After layer 1: 1 2.5 1800 370 2 12.8 After layer 2: 1 2.5 1800 370 213.5 Coupon 4 After layer 1: 1.5 2.5 1700 370 2 12.8 After layer 2: 1.52.5 1700 370 2 14.3

The results of a wear test with ASTM procedure “A” are shown in Table 4(for coupon #3 which was the best). TABLE 4 DRY SAND/RUBBER WHEEL WEARTEST ASTM G 65 PROCEDURE “A” Periodic Re-qualification of Apparatus NBSStandard Reference Material 1857 Abrasive Wear Standard D-2 Tool SteelSN: 430B Requirement: 0.324 g ± 0.030 g loss Actual: 0.310 g TEST DATALocation Conditioned Surface Initial Mass (g) 171.339 Final Mass (g)171.220 Mass Loss (g) 0.119 G65 results coupon #3

The hatch distance has important influence on the G65 results. FIG. 12shows a ground coupon (from ASTM 65) that was made with a hatch distanceof 2 mm (same as in Table 2). The result of the G65 abrasive wear testfor coupon 3 is shown in Table 3. The total mass loss was far too high,since the goal is 0.05 g or less. One reason was the hatch distance. Thematerial was washed out in between the single tracks. The phenomena isclearly visible in FIG. 12. The overlap is not enough. Therefore thisparameter was changed to 1 mm and is shown in FIG. 9.

Another problem that occurred was delamination of the first layer to thesubstrate and of the second layer to first layer where samples weredouble layer cladded. The reason was found to be in the diamond contentin the layer. More delamination occurs with a higher diamond content.These observation were applied for cracking as well.

Tables 5 and 6 show the results with Coupons #5 to #9 using the singlegas nozzle 22. The mass loss was 0.033 for Coupon #6 which was muchbetter than the goal of 0.05. TABLE 5 Diamond Cladding, February 2005Laser: Nd:YAG (400 μm fiber, Focus distance 205 mm, Spot size 3˜4 mm)Alloy: CuSn20Ti13 premixed, 100-325 mesh size screened Diamond: naturaldiamonds Z focus = 205 mm One side shield gas Substrate: White iron,thickness 11.40 mm Rotation Rotation Hatch Thickness Diamond Alloy PowerF distance [mm] [rpm] [rpm] [W] [mm/min] [mm] Coupon 5 After 2 3 2.3 7001 Short layer 1: axis 12.9 Coupon 6 After 3 3 2.3 700 1 Short layer 1:axis 13.0 Coupon 7 After 4 3 2.2 700 1 Short layer 1: axis 13.2 Coupon 8Thick 3 3 2.2 650 1 50% uneven 100 m Coupon 9 Thick 3 4 2.2 650 1 50%uneven 100 m Powder feed rates Diamond Alloy Rpm g/min Rpm g/min 1 1.1 12 2 2 2 3.8 3 2.8 3 5.4 4 7.4

The samples were also wear tested as shown in Table 6 for Coupon #6TABLE 6 DRY SAND/RUBBER WHEEL WEAR TEST ASTM g 65 PROCEDURE “A” PeriodicRe-qualification of Apparatus - Date Mar. 9, 2005 NBS Standard ReferenceMaterial 1857 Abrasive Wear Standard D-2 Tool Steel SN: 430B Requirement0.324 g ± 0.030 g loss Actual 0.304 g TEST DATA Location Surface InitialMass (g) 172.885 Final Mass (g) 172.852 Mass Loss (g) 0.033 G65 resultscoupon #6

Additional experiments were performed as follows:

Laser

Laser: Nd:YAG (400 μm fiber, working distance 221 mm).

Material

Alloy: CuSn20Til3 premixed, 100-325 mesh size screened. Drying at 60Celsius under Argon atmosphere. Diamond: natural diamonds, mesh 200-230(MANT). Powder hopper disk rotation speed versus measured powder massflow for two materials Diamond Alloy Rotation Powder mass Rotation AlloyPowder mass Diamond [rpm] flow diamond [rpm] flow Alloy 1 1.4 1 2.2 22.2 2 3.8 3 3.4 3 5.8

Nozzle

Nozzle orifice=1.7 mm (measured)

Nozzle distance to spot center about 15 mm (measured with nozzle master)

Position Unit

X=+6

Y=middle

Z=24.5

Gas Parameter:

Ar+ pressure bottle 20 psi

Flow meter shield gas nozzle: 4 (full open)

Flow meter shield gas nozzle behind 20 (nozzle 5 mm above surface)

Table 7 shows the results of further refinement of the process forCoupons 10 to 23. TABLE 7 Cladding white iron coupons Substrate: Whiteiron, thickness 11.40 mm Rotation Rotation Hatch Thickness Diamond AlloyPower F distance [mm] [rpm] [rpm] [W] [mm/min] [mm] G65 Coupon 1-1.2 2 31500 700 1.7 Short axis 10 Coupon 1-1.2 2 3 1500 700 1.7 Short axis 11Coupon 1-1.2 2 3 1500 700 1.7 Short axis 0.032 12 Coupon 1-1.2 2 3 1500700 1.7 Short axis 13 Coupon 1.5 3 3 1500 700 1.7 Short axis 14delamination Coupon 1.5 3 3 1600 700 1.7 Short axis 0.078 15 Coupon 1.22.5 3 1700 700 1.6 Short axis 0.02 16 Coupon 1.2 2.5 3 1700 700 1.6Short axis 17 Coupon 1 2.5 2.5 1700 700 1.5 Long axis 0.051 18 Coupon 12.5 2 1600 700 1.5 Long axis 0.03 19 Coupon 1 3 2.5 1600 700 1.6 Longaxis 0.056 20 Coupon 1 3 2.5 1600 700 1.6 Short axis 0.053 21 Coupon 1 32.5 1600 700 1.6 Short axis 22 Coupon 1 3 2.5 1600 700 1.6 Short axis 23

The G65 results for Coupon 16 are more than double the goal of 0.05 massloss. FIG. 13 shows the comparative G65 test results for various of thecoupons. A comparison of the wear test results over several months isshown in FIG. 13. The coatings were improved in order to reach wellbeyond the goal of 0.05 g mass loss for use in the tar sand pump.

Pumps

FIG. 10 shows hard coating of an inlet suction liner 101 (FIG. 4) inletof a pump using a robotic system 200. The outer diameter of the liner is54 inches (134 cm) and the mass is 1.5 tons (1455 kg). This is asignificant wear area in the pump of FIG. 6 as is the inlet pipe 202 ofFIG. 6A. The separated pump parts are shown in FIG. 6B.

High productivity requires an appropriate robotic cladding unit andsufficient laser beam power; and capabilities to handle large andcomplex parts. For the pump impeller 100 (FIG. 3), and suction liner 101(FIG. 4), and housing 102 (FIG. 5) the apparatus is robot system with acombined rotation axes (FIG. 10). Powder nozzles (FIG. 8) with the laserbeam can be tilted to accommodate the article which in this case is apump suction liner. This apparatus is essential for hard coating theimpeller 100. This provides a solution for the suction liners 101 aswell as impellers 100 and housings 102 in pumps as in FIGS. 3 to 5. FIG.6 shows the pump 200 with pumping for the outlet in a system 201 and theinlet 202. The inlet and outlet pipes 201 and 202 to the pump of FIG. 6are shown. FIGS. 6A and 6B show a coating around the inlet and outlet.The preferred horizontal slurry pumps are Weir Minerals (includesWARMAN) Weir Netherlands BV, the Netherlands, GIW Industries, Grovetown,Ga. and Sulzer Chemtech, Winterthur, Switzerland.

A coaxial cladding unit (Koax 8, Fraunhofer IWS, Dresden, Germany) suchas shown in FIGS. 1, 2 and 8 can be used to coat the pump parts. Forthis unit: Optimal grain size—20 to 150 μm—other sizes are possible.Recommended powder feeding rates 2 to 10 g/min. The named rates refer to1 kW laser power. Higher values are possible. Minimum powderfocus—approximately 1.0 to 2 mm. distance nozzle—working surface—13 mm.Maximum power—4 kW (diode laser) higher laser power may decrease thelong-term stability. Compatible laser —CO₂, Nd:YAG, diode laser.Dimensions—height: 80.0 mm; diameter: 78.0 mm. Note—The named values arerecommendations, for which the cladding unit was optimized. Deviatingvalues may possible but can harm the unit. Connection—4 connections forpowder feeding, inclined; 1 connection for inert gas, inclined; 2connections for cooling water (flow by room temperature); allconnections for flexible tube with 6 mm external diameter. Included indelivery—X-Y-Z positioning unit; exchangeable flange for different focusdistance; 1 exchangeable nozzle tip couple (water cooling also in theexchangeable nozzle tip).

It is intended that the foregoing description be only illustrative ofthe present invention and that the present invention be limited only bythe hereinafter appended claims.

1. An article of manufacture which comprises: (a) a ferrous substratecomprising carbon which requires a hard faced surface coating to reducewear in use; and (b) a layer of a composite which provides the hardfaced surface coating comprising diamond particles in a metal matrixwhich is bonded on the diamond particles, and wherein the layer isbonded to the substrate.
 2. The article of manufacture of claim 1wherein the diamond particles are between about 40 and 100 microns intheir largest dimension.
 3. The article of manufacture of claim 1wherein the matrix comprises copper, tin and titanium.
 4. The article ofmanufacture of claim 3 wherein the matrix consists essentially of about60 to 80% by weight copper, 15 to 25% by weight tin and 5 to 20% byweight titanium.
 5. The article of manufacture of claim 1 wherein thereare a plurality of overlapping layers on the substrate which is 40 to80% of a single track width.
 6. The article of manufacture of claims 1,2, 3, 4 or 5, wherein the substrate is a casting of white iron or asteel comprising about 4% by weight or less of the carbon.
 7. Thearticle of manufacture of claim 1 wherein the diamond particles arenaturally derived.
 8. The article of manufacture of claim 1 wherein thediamond particles are synthetically derived.
 9. A process for providingan article of manufacture with a hard faced surface coating whichcomprises: (a) providing a ferrous substrate containing carbon andrequiring a hard faced surface coating; (b) feeding a particulatemixture of diamond particles and separating metal particles which can bemelted to provide a matrix around the diamond particles into a heatingzone while impacting the mixture with a laser beam in a non-reactiveatmosphere so as to form the hard faced surface coating as a layerbonded to the substrate and the diamond particles.
 10. The process ofclaim 9 wherein the process is conducted at a temperature between about400° C. and 900° C. so as to melt the matrix and bond the diamondparticles and the matrix to the substrate, and where the rapid coolingof the process prevents decomposition of the diamond particles.
 11. Theprocess of claim 9 or 10 wherein the metal particles comprise copper,tin and titanium.
 12. The process of claim 9 or 10 wherein the metalparticles which provide the coating are about 60 to 80% by weightcopper, 15 to 25% by weight tin and 5 to 20% by weight titanium.
 13. Theprocess of claim 9 or 10 wherein the diamond particles comprises 30 to50% by volume of the metal particles.
 14. The process of claim 9 or 10wherein multiple of the layers are formed on the substrate.
 15. Theprocess of claim 9 or 10 wherein the substrate is a white iron or asteel comprising 4% or less by weight of the carbon.
 16. The process ofclaim 9 or 10 wherein the atmosphere is argon.
 17. The process of claim9 or 10 wherein the particles are applied through moving a head orarticle which is robotically driven or a CNC controlled system, whichhead supplies the particles and the laser beam on the substrate in acontinuous stream so that the layer is applied as adjacent overlappinglines on the substrate.
 18. An apparatus for hard faced surface coatinga ferrous metal substrate containing carbon which comprises: (a) a firstsupport means for holding the substrate; (b) a supply means mounted on asecond support means adjacent the first support means for supplyingdiamond particles with particles of a metal matrix onto the substrate ina heating zone which is heated by a laser beam to provide the heat,wherein the first and the second support means are adjacent to eachother and moveable relative to each other and wherein in use the laserbeam bonds the diamond particles onto the substrate at a temperaturecontrolled so as to not degrade the diamond particles to provide thehard faced surface coating in the metal matrix as the hard faced surfacecoating.
 19. The apparatus of claim 18 wherein the first support meansis moveable and mounts a head for supplying the laser beam and theparticles and the second support means is fixed.
 20. In a pumpcomprising a rotatable fluid impeller and a housing supporting animpeller for rotation in the housing for the pumping, the improvementwhich comprises at least one surface inside of the pump with a hardfaced surface coating which engages the fluid to be pumped, wherein thesurface which is coated comprises a ferrous composition comprisingcarbon and wherein coating comprises a layer of a composition comprisingdiamond particles in a metal matrix which is bonded to the diamondparticles, and wherein the layer is bonded to the substrate.
 21. Thepump of claim 20 wherein a face of an inlet plate which diverts flow ofthe fluid to the impeller has the hard faced surface coating.
 22. Thepump of claim 20 or 21 which comprises a white cast iron.
 23. The pumpof claim 20 wherein portions of the housing, the impeller and a diverterplate in the inlet of the pump comprise the hard face coating.
 24. In amethod of pumping a fluid containing abrasive particles, the improvementwhich comprises: (a) providing a pump comprising a rotatable fluidimpeller and a housing supporting the impeller for the rotation in thehousing for pumping, wherein at least one surface in the pump whichengages the fluid to be pumped has a hard faced surface coating, whereinthe surface which is coated comprises a ferrous composition comprisingcarbon and wherein the coating comprise at least one layer of acomposition comprising diamond particles and a metal matrix bonded tothe diamond particles, and wherein the layer is bonded to the substrate;(b) pumping the fluid in the pump, wherein the layer of the coatinginhibits erosion by the abrasive particles.
 25. The method of claim 24wherein the abrasive particles are in a tar sand which is transported inan aqueous solution from a mining site.
 26. The method of claim 24 or 25wherein the pump comprises cast white iron on the surfaces in contactwith the fluid and abrasive particles.
 27. The method of claim 24wherein portions of the housing, the impeller and a suction liner for aninlet of the pump comprise the hard face coating.
 28. In a pumpingsystem comprising a rotatable fluid impeller and a housing supportingthe impeller for the rotation in the housing for pumping and piping, theimprovement which comprises at least one surface inside of the pump andoptionally portions of the piping in the system with a hard facedsurface coating which engages the fluid to be pumped, wherein thesurface which is coated comprises a ferrous composition comprisingcarbon and wherein coating comprises a layer of a composition comprisingdiamond particles in a metal matrix which is bonded to the diamondparticle, and wherein the layer is bonded to the substrate.
 29. Thepumping system of claim 28 wherein a face of an inlet plate whichdiverts flow of the fluid to the impeller has the hard faced surfacecoating.
 30. In a method of pumping a fluid in a pumping systemcontaining abrasive particles, the improvement which comprises: (a)providing a pump in the pumping system with piping comprising arotatable fluid impeller and a housing supporting an impeller for andoptionally portions of piping in the system the rotation, wherein atleast one surface in the pump and optionally portions of piping in thesystem which engages the fluid to be pumped has a hard faced surfacecoating, wherein the surface which is coated comprises a ferrouscomposition comprising carbon and wherein the coating comprise at leastone layer of a composition comprising diamond particles and a metalmatrix bonded to the diamond particles, and wherein the layer is bondedto the substrate; (b) pumping the fluid in the pumping system, whereinthe layer of the coating inhibits erosion by the abrasive particles. 31.The method of claim 30 wherein the abrasive particles are in a tar sandwhich is transported in an aqueous solution from a mining site.
 32. Theprocess of claim 1 wherein the ferrous substrate is sized to provide aheat sink for the heating zone.